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|  MIL-P-18547A(SHIPS)
3.6.9 Drains.- The bottom of all pump casings or heads shall be provided with a rain connection.
d
Drains shall be fitted to drip pockets.
3.6.10 Casings and heads. -
3.6.10.1 Casings, also referred to as cylinders, are those parts which enclose the rotors. The bores of
the casing are parallel to the rotors.
3.6.10.1.1 Casing liners, also referred to as rotor housings, are replaceable parts located between the
casing bore and the rotors. Casing liners, or casings if not fitted with liners, are wearing parts,
3.6.10.2 Casings shall be made as light as possible consistent with strength and shall be ribbed and
braced on the outside as necessary to give stiffness and rigidity under the working pressure. The interiors
shall be smooth cored with easy bends wherever the direction of flow is changed.
3.6.10.2.1 It is preferred that pump casings be equipped with easily removable liners. However, consid-
eration will be given by the bureau or agency concerned to pumps not having this feature. Either liners or
casings shall be supplied as repair parts as recommended in 6.3.
3.6.10.3 Suction and discharge openings shall be cast integral with the casings, heads, or outlet elbows,
and shall be located as approved by the bureau or agency concerned.
3.6.10.4 The heads shall have accurately machined faces in accordance with MIL-STD- 10. Joints between
casings and heads may be made up either metal to metal, or with a thin plant or animal fiber gasket in accord
ante with HH-P-96, not exceeding 0.010 inch in thickness. Heads shall be rabbetted or doweled to the casings.
3.6.10.5 Forcing bolts and lifting bolts shall be provided as necessary for convenient handling during
overhaul.
3.6.11 Rotors and shafts. -
3.6.11.1 All rotors shall be accurately finish machined or ground throughout. They shall be integral with
secured to the shafts by keys or other method approved by the bureau or agency concerned. Rotors shall
secured positively against lateral displacement on shafts.
3.6.11.2 Means shall be provided for the escape of the liquid pumped from all points between rotors or
gear teeth where it may be trapped during operation and thereby create a dangerously high pressure. Means
of entrapment relief shall be approved by the bureau or agency concerned.
3.6.11.3 Deflector rings, or other similar method approved by the bureau or agency concerned, shall be
used to prevent leakage from the stuffing boxes running along the shafts. The use of felt seal rings only are
not approved. If authorized by the bureau or agency concerned, in combination with other methods, they shall
be installed so that they can be replaced without dismantling the pump.
3.6.11.4 All shafts shall be accurately machined and ground. Means shall be provided on the driven or
driving shaft of each unit so that a portable tachometer may be quickly and easily applied unless a revolution
counter is permanently installed. Either the tachometer or revolution counter shall be of a type which is sat-
isfactory to the bureau or agency concerned. Provision for the use of a tachometer will not be required on
pumps driven by alternating current motors. Shafts shall have a minimum hardness of 275 Brinell.
3.6.12 Timing gears. - Timing gears may be of the spur or double helical type. Timing gears of steel
shall be case hardened to a minimum depth of 0.0625 inch and shall have a 57 to 63 Rockwell "C" hardness.
Gears shall be fully enclosed and adequately lubricated. Timing gears shall be secured to the shafts so as to
prevent either radial or lateral movement. The method shall be approved by the bureau or agency concerned.
3.6.12.1 Provision shall be made for replacement of timing gears in the field, so that it will be satisfac-
tory to carry and replace individual parts of rotating elements. The method of installing and timing the timing
gears shall be thoroughly explained, with sketches if necessary, in the manuals (see 3.9).
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